U.S. Embassy in Bogota issues a statement condemning 'threats and recent attacks.' Last year, about 20 union leaders were killed and 90 kidnapped.

CALI, Colombia — Union organizer Juan Carlos Perez saw two gunmen in front of his house and tried to escape though the back door. But he was killed minutes later — in front of half a dozen horrified co-workers — when the assassins caught up to him at a rural bus stop. They then nonchalantly drove away on their motorbikes, witnesses of the Jan. 28 slaying said.

Perez, a 30-year-old sugar cane cutter, had been fighting for better working conditions for 1,000 workers at La Cabana sugar mill in Guachene, south of Cali, a facility with a history of labor unrest. Fellow workers said his goals included direct negotiations with management and steady paychecks.

"He felt affected by the poor treatment of the workers and that they should unite to demand better conditions," his widow, Luz Aidee, who was left with children ages 7 and 11, said in an interview. "He was not the type to make scandals or insult anyone. But he was not one to be intimidated either."

Last year, about 20 union leaders were killed in Colombia, with few if any of the slayings resulting in arrests. In addition, 90 labor leaders were kidnapped and 431 labor leaders were threatened, according to CUT, the nation's labor umbrella organization.

On Feb. 23, one of the nation's top labor leaders, Luis Miguel Morantes, head of the Colombian Workers Confederation, narrowly escaped assassination in Cali. Men on motorbikes opened fire on his armored car while he was in town attending a meeting of a union representing workers of Emcali, the local power utility.

In an unusual gesture, the U.S. Embassy in Bogota issued a statement Friday condemning "threats and recent attacks against union members in Cali," saying a focus by the attorney general on the cases is "essential for the adequate investigation and prosecution of these cases."

Colombia has long had one of the world's worst records in protecting labor union officials, a sticking point before last year's signing of the U.S.-Colombia free trade agreement. Since 1986, more than 2,900 labor officials have been slain and nearly 5,700 threatened, according to CUT statistics.

Yielding to pressure from U.S. labor groups and the U.S. trade representative, Colombia agreed in 2011 to tighter protection measures under a deal signed by President Obama and Colombian President Juan Manuel Santos. It bolstered a national protection unit set up in the 1990s to shield threatened journalists and labor and human rights leaders.

Since then, killings of labor leaders have dropped significantly, from 70 or more annually common in the decade before Santos took office in 2010, a reduction that U.S. labor leaders and human rights groups have recognized as a sign of progress.

At the same time, threats have been on the increase, indicating that workers feel more secure about lodging complaints but also a sign that certain employers, rival owner-vetted unions and mafias who see their longtime hold over Colombian labor in jeopardy are ratcheting up an intimidation campaign, analysts say.

"There is a long anti-union tradition in Colombia among businesses, the government and even the public in general," said Luciano Sanin, director of the National Labor Academy, a Medellin-based civil society group. "But it's a mistake to think it's a problem of the past. Unions are still not accorded a role in the democratic process."

"There have been some steps forward but the fact that the number of threats is up shows that the campaign of terror is far from over," said Celeste Drake, the AFL-CIO's trade and globalization specialist in Washington.

"The Santos administration has made some tentative advances but needs to do more," said Lisa Haugaard, of Washington-based Latin America Working Group, a human rights watchdog active in Colombia.

Stronger laws weren't much help to Perez. A few days before he was killed, he interceded in an argument between a sugar mill supervisor and a co-worker who was trying to distribute leaflets to publicize a union meeting. The action may have cost him his life, said a fellow union official who, fearful for his life, spoke on condition of anonymity.

"He told the boss the workers had a perfect right under Colombian law to tell people about the meeting," the co-worker said. No suspects have been arrested and managers at the La Cabana sugar mill did not respond to an emailed request for an interview.

Asked to explain Colombia's historically poor record in securing labor rights, Clara Lopez, a Harvard-educated economist and president of the left-wing Democratic Pole Party, said that it has to do with ingrained intolerance for unions.

"It's part of a bigger issue. In Colombia it's safer to form a guerrilla group or a criminal band than a labor union," Lopez said. "Big business does not take well to unions, and the government doesn't have a strong enough stance to make the companies comply."

Said the AFL-CIO's Drake, "In Colombia, it's about those on top staying on top, and those on the bottom staying there."